The present invention concerns object-sensor-based fluid-flow control. It has particular, although not exclusive, application to flow-control systems in which the object to be sensed is located in an environment that is relatively hostile to the typical object sensor.
Automatic faucets and flushers for urinals and water closets typically operate in response to an object sensor. A typical installation employs an infrared-radiation source, such as a light-emitting diode, and an infrared-radiation sensor, such as a PIN diode circuit, that detects objects by sensing infrared radiation that reflects off the object.
Although such systems are simple in concept, certain practical considerations conspire to make them expensive to implement. The main factor is that the object tends to be located in an environment that is somewhat hostile to electronic sensor circuitry. An automatic-faucet user's hands, for instance, which are typical objects for the system to detect, are located in a water stream. This results in splashing and high humidity. The sensor mechanism must therefore be designed to withstand these environmental factors. Moreover, since automatic-faucet installations tend to be in public areas, they are particularly subject to rough treatment and even vandalism. A system designed to withstand these environmental factors has typically been relatively expensive.